腰围比体重指数更能反映健康风险.pdf

See corresponding editorial on page 347.Waist circumference and not body mass index explains obesity- related health risk1–3Ian Janssen, Peter T Katzmarzyk, and Robert RossABSTRACT Background: The addition of waist circumference (WC) to body massindex(BMI;inkg/m2)predictsagreatervarianceinhealthrisk than does BMI alone; however, whether the reverse is true is not known. Objective:WeevaluatedwhetherBMIaddstothepredictivepower of WC in assessing obesity-related comorbidity. Design:Subjectswere14 924adultparticipantsinthethirdNational Health and Nutrition Examination Survey, grouped into categories ofBMIandWCinaccordancewiththeNationalInstitutesofHealth cutoffs. Odds ratios for hypertension, dyslipidemia, and the meta- bolic syndrome were compared for overweight and class I obese BMI categories and the normal-weight category before and after adjustment for WC. BMI and WC were also included in the same regression model as continuous variables for prediction of the met- abolic disorders. Results: With few exceptions, overweight and obese subjects were more likely to have hypertension, dyslipidemia, and the metabolic syndrome than were normal-weight subjects. After adjustment for WC category (normal or high), the odds of comorbidity, although attenuated,remainedhigherinoverweightandobesesubjectsthanin normal-weight subjects. However, after adjustment for WC as a continuous variable, the likelihood of hypertension, dyslipidemia, andthemetabolicsyndromewassimilarinallgroups.WhenWCand BMI were used as continuous variables in the same regression model, WC alone was a significant predictor of comorbidity. Conclusions: WC, and not BMI, explains obesity-related health risk.Thus,foragivenWCvalue,overweightandobesepersonsand normal-weight persons have comparable health risks. However, when WC is dichotomized as normal or high, BMI remains a sig- nificant predictor of health risk.Am J Clin Nutr 2004;79: 379–84.KEY WORDSAbdominal obesity, metabolic syndrome, hy- pertension, dyslipidemiaINTRODUCTIONIt has long been recognized that body mass index (BMI; in kg/m2) is a predictor of the morbidity and mortality that are due to numerous chronic diseases, including type 2 diabetes, cardio- vasculardisease(CVD),andstroke(1,2).Inaddition,ithasbeen establishedthatabdominalobesity,assessedbywaistcircumfer- ence (WC), predicts obesity-related health risk (1–4), and the weightedevidenceindicatesthatWCcoupledwithBMIpredicts health risk better than does BMI alone (3, 5–7). In fact, recent findingsindicatethatWCisastrongermarkerofhealthriskthanis BMI (4). The utility of BMI and WC in predicting obesity- related health risk has been recognized by the National Heart, Lung, and Blood Institute of the National Institutes of Health (NIH; 2). The NIH guidelines indicate that the health risk in- creasesinagradedfashionwhenmovingfromthenormal-weight through obese BMI categories, and that within each BMI cate- gorymenandwomenwithhighWCvaluesareatagreaterhealth risk than are those with normal WC values (2). Thus, it is as- sumed that BMI and WC have independent effects on obesity- related comorbidity. AlthoughitisevidentthattheadditionofWCtoBMIpredicts agreatervarianceinhealthriskthandoesBMIalone,whetherthe reverse is true is unclear. That is, for a given WC value or WC category (eg, normal or high), it is not known whether higher BMI values indicate a greater health risk than do lower BMI values. However, it has been shown that WC and hip or thigh circumference have independent and opposite effects on meta- bolic health risk. Whereas WC is positively associated with health risk, hip and thigh circumferences are negatively associ- atedwithhealthrisk(8–13).Thisimpliesaprotectiveeffectofa largehiporthighcircumference(orboth),whichcouldbedueto a greater lean mass in the nonabdominal regions. Indeed, lean bodymassisnegativelyassociatedwithall-causemortality(14). WhenthisfactiscoupledwiththeknowledgethatWCisastrong predictor of both abdominal and nonabdominal fat (15, 16), it seems reasonable to suggest that, for a given WC value, higher BMI values may not indicate an increased health risk. Address- ing this issue could have important implications for the determi- nation of the manner in which WC and BMI are used to predict obesity-related comorbidity in both the research and the clinical settings. The purpose of this investigation was to determine whether BMI adds to the predictive power of WC in assessing obesity-1From the Department of Community Health and Epidemiology (IJ andPTK), the School of Physical and Health Education (PTK and RR), and the Division of Endocrinology and Metabolism, Department of Medicine (RR), Queen’s University, Kingston, Canada. 2SupportedbytheCentersforDiseaseControlandPrevention(NHANESIII study), Heart and Stroke Foundation grant T4946 (to PTK), grants from the Canadian Institutes of Health Research (MT 13448) and Mars Corpora- tion (to RR), and a Canadian Institutes of Health Research Postdoctoral Fellowship (to IJ). 3Addre。